FCEUX vs Nes2x

FCEUX is a free, open-source emulator for NES, Famicom, Famicom Disk System, and Dendy systems. It supports NTSC, PAL, and NTSC-PAL Hybrid video modes and offers tools for casual play as well as advanced work such as debugging, ROM hacking, map making, tool-assisted movies, and Lua scripting. The project maintains Win32 and Qt/SDL ports. The Qt/SDL version runs across Windows and UNIX-like systems, including Linux, Solaris, BSD, and OSX. Its tools include debug utilities, movie recording, a TAS Editor, sprite viewer, NES Palette Editor, AVI RIFF Tree viewer, and frame timing tool. Network play in both Win32 and SDL ports is not functional, and the project says it has no plans to fix it. Building Qt/SDL requires Qt5, SDL2, minizip, zlib, and OpenGL; CMake is needed to build from source. FFmpeg libraries are optional for AVI recording, and libx264 is optional for H.264 AVI encoding. The project dates to 2006, and its home page lists version 2.6.6, released on 26 August 2023, as the latest release.

Nes2x has no write-up on Specifiction yet; its figures are above.